Bizzarre Chimes Pattern-Ridgeway Rio Grandfather

Have a 15 year old ridgeway "Rio" model with a Kelinger (sp) movement that is driving me nuts.

Pattern: It chimes fine at the top of the hour and every quarter, then misses strike at the next hour, only to continue in this fashion for a few hours more (always striking the hour at quarter past) until the chimes fall completely silent.

Sometimes raising and lowering the chimes silencer will re-start it at the top of the hour, but it always falls into the same pattern again.

Have had THREE servicemen: Two say "New Movement", one says, "Through cleaning MIGHT do it."